rustdoc: Fix position of collapse-toggle on small screens

Author: vi

src/librustdoc/html/static/rustdoc.css

@@ -1045,6 +1045,10 @@ h4 > .important-traits {
 		z-index: -1;
 		border-bottom: 1px solid;
 	}
+
+	.collapse-toggle {
+		left: -17px;
+	}
 }